Steam Assisted Gravity Drain

ABSTRACT

A steam assisted gravity drain for heavy oil, comprising a body sub-assembly having first and second ends; a top sub insertable into the body sub-assembly; a bottom sub insertable into the body sub-assembly; first and second diffuser caps encircling the top sub and the bottom sub, respectively; a plurality of radially arranged flow tubes extending between the diffuser caps and the body sub-assembly; and a sliding sleeve extending between the top and bottom subs. A method of flow conditioning for heavy oil pipelines, comprising the steps of attaching a plurality of steam assisted gravity drains in a closed position to a liner; running the drains vertically downhole into the horizontal leg of a well; and running a shifting tool downhole and selectively opening the sleeve of the drain by stabbing the shifting tool into the sleeve and pulling the sleeve back.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the preferred embodiments is provided by way of example only and with reference to the following drawings, in which:

FIG. 1 is a perspective view of the steam whistle assembly, according to the invention;

FIG. 2 is a side plan view of the steam whistle assembly in an open position, according to the invention;

FIG. 3 is a side plan view of the steam whistle assembly in a closed position, according to the invention; and

FIG. 4 is a cross-sectional view of a diffuser cap, according to the invention;

FIG. 5 is a cross-sectional view of the steam whistle assembly in a closed position, according to the invention;

FIGS. 6A-6E are cross-sectional, perspective, and plan views of the steam whistle assembly in an open position, according to the invention;

FIGS. 7A-7C are cross-sectional; plan and perspective views of the body of the assembly, according to the invention;

FIGS. 8A-8D are plan, perspective and cross-sectional views of the sub-assembly;

FIGS. 9A-9C are cross-sectional, plan and perspective views of the top sub of the assembly of the invention;

FIGS. 10A-10C are cross-sectional and plan views of the diffuser cap of the assembly of the invention;

FIGS. 11A-11C are cross-sectional and plan views of the washer of the assembly of the invention;

FIGS. 12A-12C are cross-sectional, plan and perspective views of the flow tube of the assembly of the invention;

FIGS. 13A-13C are cross-sectional, plan and perspective views of the bottom sub of the assembly of the invention; and

FIGS. 14A-14E are cross-sectional, plan and perspective views of the sliding sleeve of the assembly of the invention.

In the drawings, one embodiment of the invention is illustrated by way of example. It is to be expressly understood that the description and drawings are only for the purpose of illustration and as an aid to understanding, which are not intended as a definition of the limits of the invention.

DETAILED DESCRIPTION OF THE INVENTION

There is provided Steam Assisted Gravity Drain (“SAGD”), also referred to herein as a Steam

Whistle Flow Control Assembly, for use with heavy oil. The primary application is the oil sands in Northern Alberta, but other oil producing areas including Saudi Arabia may find application for this invention.

The improvement over prior art in the field is to introduce “flow conditioning” to the downhole tooling industry. It is used in pipeline applications where tubular devices reduce turbulent flow and promote laminar conditioning. Tubular bundles and flow plates are used in valve applications, placed a specific number of bore diameter down stream. The invention overcomes “continuous recess” or “discontinuous recess - windows” by introducing tubular members that reduce flow turbulence and swirl.

The invention further entails reduction in open hole erosion or “rat holing”, casing damage or impingement due to flow erosion effects, but most importantly, increased “thermal reach” since healing zones are further extended with laminar flow compared to turbulent.

Another technical innovation is the introduction of a two piece, welded Body which nobody uses in the industry. This reduces complicated machining and the need for specialized tooling which adds to the manufacturing cost.

Essentially the multiple devices are screwed onto the liner, spaced appropriately and run vertically downhole into the horizontal leg of the well. The device is run in the CLOSED position, meaning the Sleeve is stroked downwards so that a series of windows misalign with the recess of the Body, hence no flow through from the upper and lower ports. The operator then goes downhole with a 3 ½ B OTIS style B Shifting Tool and selectively opens the device; the tool stabs into the Sleeve and user pulls back on the coil tubing, thereby rendering OPEN the Sleeve. User may also push through the Sleeve to an assembly below a desired location and select another, and OPEN that if preferred. Alternatively, user may close an open sleeve by pushing down, simply reversing that procedure described above.

The Retaining Ring is a single piece integral component. The absence of a Breast Plate and fasteners removes any uncertainty with the device being damaged if it is hit on the trip downhole. The one piece also simplifies machining and drops the cost in manufacturing the part.

The Steam Whistle Flow Control Assembly (FCA) is a device used to maximize production efficiency by improving upon steam injection characteristics and steam-oil ratios (SOR) in SAGD applications. Flow conditioning extends heating zone length, mitigates thermal losses at the exit port, reduces open hole erosion and casing damage. These flow control improvements reduce the number of assemblies required to meet specific target location while maximizing custom steam injection rates.

The Steam Whistle FCA maximizes steam injection efficiencies along the horizontal well by exit flow conditioning. Having greater laminar exit flow extends the thermal reach beyond traditional heating zones, thus reducing the number of installations required. Laminar flow also increases the thermal steam efficiency at the delivery point while reducing open hole erosion and casing impingement associated with turbulent flows in competitor devices.

The Steam Whistle FCA offers operational choice for control of exit port numbers, OFF/ON points along the horizontal length of the installation and the option of running a traditional sliding sleeve technology without introducing specialized tooling. Attention to steam injection flow exit conditioning reduces the number of installations, increases production efficiency and maximizes operator choices to customize a balanced solution at the well, because not all holes are alike. 

What is claimed is:
 1. A steam assisted gravity drain for use with heavy oil, comprising: a body sub-assembly having first and second ends; a top sub insertable into the first end of the body sub-assembly; a bottom sub insertable into the second end of the body sub-assembly; first and second diffuser caps encircling the top sub at the first end of the body sub-assembly and the bottom sub at the second end of the body sub-assembly, respectively; a plurality of radially arranged flow tubes extending between the diffuser caps and the body sub-assembly; and a sliding sleeve extending between the top and bottom subs.
 2. A method of flow conditioning for heavy oil pipelines, comprising the steps of: a) attaching a plurality of steam assisted gravity drains in a closed position to a liner; b) running the drains vertically downhole into the horizontal leg of a well; and c) running a shifting tool downhole and selectively opening the sleeve of the drain by stabbing the shifting tool into the sleeve and pulling the sleeve back. 